Method of making 9, 10-phenanthraquinone



United States Patent 3,014,049 Patented Dec. 19, 1961 tice 3,014,049 METHOD OF MAKING 9,10-PHENANTHRA- QUINONE Edward L. Mihelic, Penn Hills Township, Allegheny County, and Myron H. Wilt, Monroeville, Pa., assignors to United States Steel Corporation, a corporation of New Jersey No Drawing. Filed Apr. 8, 1960, Ser. No. 20,815 2 Claims. (Cl. 260396) This invention relates to an improved method of making 9,10-phenanthraquinne. The compound finds utility as a mildew-proofing agent (Patent No. 2,401,028), as a polymerization inhibitor (Patent No. 2,675,914) and a dyestulf (Patent No. 543,784).

While methods are known for making 9,10-phenanthraquinone, they require costly reagents or are so low in yield that the compound has not been available commercially in large quantities. It is therefore the object of our invention to provide a method which is inexpensive and utilizes a readily available source material of low cost.

In general terms, our method comprises treating an alcohol solution of methyl Z-formyl-2'-biphenylcarboxylate with an aqueous solution of an alkali-metal cyanide. The resulting reaction produces a precipitate of 9,10- phenanthraquinone directly and the product may be readily collected by filtration. The starting material may be easily prepared by ozonization of low-cost phenanthrene. The invention therefore affords an economical source of 9,10-phenanthraquinone.

A complete understanding of the invention may be obtained from the following detailed explanation of several typical examples of the practice thereof.

Example I Methyl Z-formyl-Z'-biphenylcarboxylate (2.4 grams or millimols) was dissolved in 95% ethanol (10 ml.). To this mixture was added a solution of sodium cyanide (0.5 gram or 10 millimols) in water (5.0 ml.). The mixture was allowed to stand at room temperature for 3 hours with continuous stirring by means of a magnetic stirrer. At the end of this time, the 9,10-phenanthraquinone, which separated as a crystalline solid, was col lected by filtration. The product weighing 1.36 grams was Washed on the filter with a 1:1 ethanol-water mixture (10 ml.) followed by copious washing with water and drying at 110 C. By this process, a yield of 65% of high-quality phenanthraquinone was obtained (melting range: 205 to 208 C.).

Example 11 The procedure was the same as that described in Example I, except that potassium cyanide (0.65 gram or 10 millimols) replaced the sodium cyanide. A product yield of 1.40 gram or 67% was obtained (melting range: 206 to 208 C.).

Example III The procedure was the same as that described in Example I, except that the solvent was a corresponding methanol-water mixture, and potassium cyanide replaced the sodium cyanide. A product yield of 1.12 grams or 54% was obtained (melting range: 203 to 208 C.).

v carboxylate in a C to C saturated unsubstituted mono- 4 Example V The procedure was the same as that described in Example I, except that a corresponding'mixture of tertiary butanol and water was the solvent, and potassium cyanide replaced the sodium cyanide. The product yield was 0.77 gram or 37% over anextended reaction time of 48 hours. The product melted over the range 189 to 195 C.

The use of ethanol-water as the solvent is necessary to obtain the highest yield. The use of potassium cyanide, which gives only slightly higher yields than the sodium salt, is not economically advantageous in View of its higher cost.

A substantial decrease in yield was noted when the reaction was conducted at 50 C. or 20 C., rather than at a temperature inour preferred range, 25 to 35 C. The reduction in yield when the reaction temperature was 20 C. appeared to be the result of decreased solubility of the starting material at that temperature. When the reaction temperature was 50 C., possibly side reactions of a nature not yet determined occurred to decrease the yield.

When the total cyanide concentration was halved, either by decreasing the amount of cyanide to half a molar equivalent or by doubling the volume of solvent, the yield of product decreased from 67 to 62%.

The reaction, a condensation catalyzed by cyanide ion, results in the regeneration of the cyanide, which can be again reacted with additional starting material. This was demonstrated in a recycle procedure. After separating the initial yield of phenanthraquinone (67%), the reaction filtrate was recharged with thesame amount of methyl 2-formyl-2'-biphenylcarboxylate (2.4 grams) and reacted as above for 3 hours. The yield of product obtained was 72% with slightly decreased purity (melting A second recharge of the reaction filtrate gave a 56% yield of product. This decrease in yield is attributed to the build-up of side reaction product or products.

The equation expressing the overall reaction is as follows:

0 .iH -C=O I +CN- I +CH3OH+ON- -O-O CH3 O=O it Q g/iigitllgl 9,10-phenanthraquinone The amount of ethanol for the amount of starting material given above, may. vary from 10 to 15 ml.; the amount of water from 5 to 7 ml.; and the amount of cyanide from 0.2 to 1.0 gram. As shown by the examples the alcohol may be from C to C It will be evident from the foregoing that the invention provides a convenient economical source of 9,10-phenanthraquinone and a simple method for its production.

Although we have disclosed herein the preferred practice of our invention, we intend to-cover as well any change or modification therein which may be made without departing from the spirit and scope of the invention.

We claim:

1. A method of making 9,10-phenanthraquinone which comprises dissolving methyl 2 formyl 2"- biphenylalcohol, adding to the solution an alkali-metal cyanide and collecting the 9,10-phenanthraquinone which forms and precipitates from the solution.

4;. 2. A method as defined in claim 1, characterized by OTHER REFERENCES the amount of cyanide being at least the molar equivalent Beilstein: Handbuch der Organischen Chemie Band of the carboxylate. 7 p 797' References Cited in the file of this patent 5 7 32 53 i igig def orgamschen Chemle Band UNITED STATES PATENTS Elseviers Encyclopedia of Organic Chemistry, vol. 13, 1,288,431 Lewis et a1. Dec. 17, 1918 P- FOREIGN PATENTS Mayer: Berlchte, vol. 45, pages 1105-13 (1912).

508,526 Great Britain July 3, 1939 10 

1. A METHOD OF MAKING 9,10-PHENANTHRAQUINONE WHICH COMPRISES DISSOLVING METHYL 2-FORMYL-2''-BIPHENYLCARBOXYLATE IN A C1 TO C4 SATURATED UNSUBSTITUTED MONOALCOHOL, ADDING TO THE SOLUTION AN ALKALI-METAL CYANIDE AND COLLECTING THE 9,10-PHENANTHRAQUINONE WHICH FORMS AND PRECIPITATES FROM THE SOLUTION. 